The invention relates generally to voltage regulators and more particularly to switching regulators used to control voltage levels at a pair of outputs.
As is known in the art, switching regulators are frequently used to control the voltage at an output thereof. In one such regulator, a feedback voltage is used to produce a control signal related to the difference between the actual voltage at the output and the desired output voltage. The regulator includes an oscillator for producing a train of pulses. The duty cycle of the train of pulses is controlled or modulated in accordance with the control signal to couple a voltage source to and from an inductor in accordance with the duty cycle. Thus, the inductor periodically stores an amount of energy related to the difference between the actual and desired output voltages during the portion of each period of the pulse train when such inductor is coupled to the supply. During the remaining portion of the period, i.e., when the inductor is decoupled from the supply, the energy stored in the inductor is directed to a capacitor connected in parallel with the output to raise the voltage on the capacitor until it reaches the desired voltage, as when the actual voltage is less than desired voltage; otherwise, the capacitor discharges to the load, as when the actual voltage is greater than the desired voltage. While such switching regulator is effective in controlling the voltage at a single output, it is sometimes desirable to control different voltages at correspondingly different outputs. One way to provide such dual control would be to use two regulators; however, such is costly.